It means the Pokemon was trained in certain stats.
Battling Pokemon gives you a certain amount of EV points. For example, battling a starly gives you 1 speed EV point for the Pokemon that battled it. Different Pokemon give different EV's. EV's work like the following:
every 4 EV's you get in one stat, that stat is raised by 1. The maximum EV's you can have in any one stat is 255 and the total number of EV's your Pokemon can have is 510. So essentially, only two stats can be fully maxed. You could also divide up the EV's evenly into the stats, but that's not the best thing to do. EV-training is tedious, and without the right items, it takes forever.
Go to serebii.net for all the info about EV's.
Chat with our AI personalities
That also happened to me. But the reason why is because either you accidentally entered the stats wrong or you accidentally EV trained your Pokemon when you were battling with it. When you're simply raising Pokemon, they could get EV's by accident. Since EV's are invisible, you can't determine why this happened. And the IV Calculators require you to enter in EV's so it can calculate the average IV's. For help on EV's, try this searching this on google: "What are EV's?"
train them without using rare candy's
EVs stand for Effort Values. They are how much of a stat your Pokemon earns when it levels up. If you wish to work on a single stat, fight certain Pokemon. If you level up by fighting a lot of Starlys, you will get lots of the speed EVs, giving your Pokemon more of the speed stat. Those items like Proetin and Iron also give you EVs. If you EV train your Pokemon a lot they will become very powerful.
depends on the nature the Pokemon haves:P:P
Train it as you train all pokemon.